Irreversible Formation Research Articles

SCSC Transformation and Post-Synthesis Modification of MOFs with Proton Conduction and Ratiometric Fluorescence-Sensing Properties.

The modification of metal-organic framework (MOF) materials to facilitate their practical applications is an extremely challenging and meaningful topic. In this work, two stepwise modification strategies for MOFs were conducted. First, we have demonstrated a single-crystal-to-single-crystal (SCSC) transformation from a microporous three-dimensional (3D) MOF to a two-dimensional (2D) coordination polymer (CP). The centrosymmetric [Cd(3-bpdb)(MeO-ip)]n (1) transforms into a chiral [Cd2(3-bpdb)(MeO-ip)2(CH3OH)2]n (2), which is triggered by the reaction time with methanol that acts as a structure-directing agent. The conversion relationship of 1 to 2 at different reaction times was studied in detail. Density functional theory (DFT) calculations clearly state that the irreversible formation of 2 is thermodynamically favorable. Intriguingly, 2 exhibits good proton conduction of 1.34 × 10-3 S cm-1 under 363 K and 98% relative humidity (RH) due to unique H-bond network characteristics. To the best of our knowledge, there are very few cases of 3D to 2D SCSC transformation stimulated by reaction time. The results have important implications for understanding the SCSC transformation mechanism and synthetic chemistry. On the other hand, the lanthanide3+-functionalized hybrids (Ln3+-MOF), Ln3+@1, were continuously prepared by incorporating luminescent Ln3+ ions into the structure of 1 through encapsulating post-synthesis modification (PSM). Tb3+@1 exhibits double emission in water and shows visual ratiometric fluorescence behavior for sensing glutamic acid (Glu), tryptophan (Trp), and Al3+, which is more reliable and accurate than single emission. Our work may not only provide new insights into the multiple modification of MOF materials but also promote the practical application of such materials.

Recent Progress in Aqueous Zinc-Ion Batteries: From FundamentalScience to Structure Design.

Rechargeable aqueous zinc-ion batteries (ZIB) sparked a considerable surge of research attention in energy storage systems due to its environment benignity and superior electrochemical performance. Up to now, less efforts to delve into mechanisms of zinc metal anode and their electrochemical performance. Zn metal anodes sustain thorny issues with Zn dendrite growth, hydrogen evolution reaction, and Zn corrosion irreversible byproduct formation, which results in low coulomb efficiency (CE) and poor cycle ability of the battery. Herein, we reveal the fundamental understanding of the above issue, outline four step, including mass transfer, desolvation process, charge transfer and Zn cluster formation. It can be clearly seen from reported strategies to promote Zn anode stability that deals with one or more steps, thereby boosting the understanding of the issues of Zn anodes and benefiting the rational design to surmount the issue. We also sum up advanced materials and structure design such as the design of the anode surface and internal structure, electrolyte strategies, and multifunctional separators. Finally, possible tactics and future innovation direction for Zn-based batteries are proposed to achieve high performance aqueous Zinc-ion batteries.

Time‐average stochastic control based on a singular local Lévy model for environmental project planning under habit formation

This study applies the theory of stochastic control to an environmental project planning to counteract against the sediment starvation problem in river environments. This can be considered as a time‐average inventory problem to time‐discretely control a continuous‐time system driven by a non‐smooth jump process under habit formation disturbing project implementation. The system is modeled such that the sediment storage dynamics are physically consistent with certain experimental results. Further, the habit formation is modeled as simple linear dynamics and serves as a constraint related to the replenishment amount of the sediment. We show that the time‐average control problem is not necessarily ergodic. Consequently, the effective Hamiltonian may become a non‐constant. Thereafter, ratcheting cases as extreme cases of the irreversible habit formation are considered, owing to them being unique exactly solvable non‐ergodic control problems. The optimality equation associated with a regularized and hence well‐defined control problem is verified. Furthermore, a finite difference scheme is examined against the exactly solvable case and then applied to more complicated cases.

Investigation of Three-Dimensional Bacterial Adhesion Manner on Model Organic Surfaces Using Quartz Crystal Microbalance with Energy Dissipation Monitoring.

Bacterial biofilms reduce the performance and efficiency of biomedical and industrial devices. The initial step in forming bacterial biofilms is the weak and reversible attachment of the bacterial cells onto the surface. This is followed by bond maturation and secretion of polymeric substances, which initiate irreversible biofilm formation, resulting in stable biofilms. This implies that understanding the initial reversible stage of the adhesion process is crucial to prevent bacterial biofilm formation. In this study, we analyzed the adhesion processes of E. coli on self-assembled monolayers (SAMs) with different terminal groups using optical microscopy and quartz crystal microbalance with energy dissipation (QCM-D) monitoring. We found that a considerable number of bacterial cells adhere to hydrophobic (methyl-terminated) and hydrophilic protein-adsorbing (amine- and carboxy-terminated) SAMs forming dense bacterial adlayers while attaching weakly to hydrophilic protein-resisting SAMs [oligo(ethylene glycol) (OEG) and sulfobetaine (SB)], forming sparse but dissipative bacterial adlayers. Moreover, we observed positive shifts in the resonant frequency for the hydrophilic protein-resisting SAMs at high overtone numbers, suggesting how bacterial cells cling to the surface using their appendages as explained by the coupled-resonator model. By exploiting the differences in the acoustic wave penetration depths at each overtone, we estimated the distance of the bacterial cell body from different surfaces. The estimated distances provide a possible explanation for why bacterial cells tend to attach firmly to some surfaces and weakly to others. This result is correlated to the strength of the bacterium-substratum bonds at the interface. Elucidating how the bacterial cells adhere to different surface chemistries can be a suitable guide in identifying surfaces with a more significant probability of contamination by bacterial biofilms and designing bacteria-resistant surfaces and coatings with excellent bacterial antifouling characteristics.

A new electrochemical method that mimics phosphorylation of the core tau peptide K18 enables kinetic and structural analysis of intermediates and assembly

Tau protein's reversible assembly and binding of microtubules in brain neurons are regulated by charge-neutralizing phosphorylation, while its hyperphosphorylation drives the irreversible formation of cytotoxic filaments associated with neurodegenerative diseases. However, the structural changes that facilitate these diverse functions are unclear. Here, we analyzed K18, a core peptide of tau, using newly developed spectroelectrochemical instrumentation that enables electroreduction as a surrogate for charge neutralization by phosphorylation, with simultaneous, real-time quantitative analyses of the resulting conformational transitions and assembly. We observed a tipping point between behaviors that paralleled the transition between tau's physiologically required, reversible folding and assembly and the irreversibility of assemblies. The resulting rapidly electroassembled structures represent the first fibrillar tangles of K18 that have been formed invitro at room temperature without using heparin or other charge-complementary anionic partners. These methods make it possible to (i) trigger and analyze in real time the early stages of conformational transitions and assembly without the need for preformed seeds, heterogenous coacervation, or crowding; (ii) kinetically resolve and potentially isolate never-before-seen early intermediates in these processes; and (iii) develop assays for additional factors and mechanisms that can direct the trajectory of assembly from physiologically benign and reversible to potentially pathological and irreversible structures. We anticipate wide applicability of these methods to other amyloidogenic systems and beyond.

Changes in water-vapor-adsorption isotherms of pulp fibers and sheets during paper recycling, including drying of wet webs, and disintegration and sonication of dried sheets in water

Abstract A never-dried (ND) fines-free softwood bleached kraft pulp was converted to air-dried and thermally dried handsheets, which were then disintegrated or sonicated in water under various conditions. These disintegrated or sonicated pulps were converted to handsheets and used to obtain fundamental data on paper recycling. The water-vapor-adsorption isotherms of the pulp and sheet samples after super-critical-point drying showed clear differences between the water volumes adsorbed by the ND pulp, once-dried pulp, and dried sheets at the same relative humidities above 50%. These differences are caused by hornification of the pulp and sheet samples during drying and recycling. Air and thermal drying of wet webs decreased the adsorbed-water-vapor volume by 7%–9% and 14%–18%, respectively, relative to that adsorbed by the original ND pulp. We hypothesize that the decrease in water-vapor-adsorption volume from that of the original ND pulp at relative humidities >50% reflects the degree of irreversible formation of hydroxyl groups in the originally hydrophilic hemicelluloses and crystalline cellulose microfibril surfaces in the pulp and sheet samples during drying and paper recycling. The water-vapor-adsorption isotherms of pulp and sheet samples can be used to quantify the degree of hornification or the amount of irreversible hydrogen bonds formed during paper recycling.

Highly stabilized single-crystal P2-type layered oxides obtained via rational crystal orientation modulation for sodium-ion batteries

The development of P2-type Na–Ni–Mn oxides as high-voltage cathode materials for sodium-ion batteries is being extensively researched. However, achieving good electrochemical reversibility for such oxides at high voltage remains challenging. Herein, highly dispersed hexagonal-prism-like single-crystal P2-type Na0.66Ni0.26Zn0.07Mn0.67O2 (MC-NNZM) with a high proportion of {001} planes is synthesized through a combined coprecipitation and molten-salt method. The presence of molten Na2SO4 and the low surface energy of {001} planes are critical in forming the anisotropic single-crystal structure. In the 2.0–4.4 V voltage window, MC-NNZM exhibits a reversible capacity of 122.1 mAhg−1 with a median discharge voltage of 3.5 V at 10 mA g−1. Moreover, the capacity retentions of MC-NNZM reach 95.8% and 98.3% in the 2.0–4.4 V and 2.0–4.3 V voltage ranges after 100 cycles at 100 mA g−1, respectively. Electrochemical in situ X-ray diffraction patterns reveal that, because of the {001}-dominated single-crystal structure, the gliding of transition metal oxide slabs in the high-voltage region is effectively restrained; subsequently, this significantly mitigates the volume change of MC-NNZM during cycling. Consequently, unlike layered oxides with random crystal orientation, MC-NNZM is effectively resistant to mechanical fracture without the irreversible formation of intragranular cracks and dislocations after extensive cycling, thus avoiding continuous electrolyte decomposition on the material surface and stabilizing efficient ionic/electronic transport paths in the cathode. This work paves a new avenue for improving the cycling stability of P2-type layered oxides with a high upper-cutoff voltage based on a single-crystal structure formed via rational crystal orientation modulation.

Virtual screening, identification and in vitro validation of small molecule GDP-mannose dehydrogenase inhibitors.

Upon undergoing mucoid conversion within the lungs of cystic fibrosis patients, the pathogenic bacterium Pseudomonas aeruginosa synthesises copious quantities of the virulence factor and exopolysaccharide alginate. The enzyme guanosine diphosphate mannose dehydrogenase (GMD) catalyses the rate-limiting step and irreversible formation of the alginate sugar nucleotide building block, guanosine diphosphate mannuronic acid. Since there is no corresponding enzyme in humans, strategies that could prevent its mechanism of action could open a pathway for new and selective inhibitors to disrupt bacterial alginate production. Using virtual screening, a library of 1447 compounds within the Known Drug Space parameters were evaluated against the GMD active site using the Glide, FRED and GOLD algorithms. Compound hit evaluation with recombinant GMD refined the panel of 40 potential hits to 6 compounds which reduced NADH production in a time-dependent manner; of which, an usnic acid derivative demonstrated inhibition six-fold stronger than a previously established sugar nucleotide inhibitor, with an IC50 value of 17 μM. Further analysis by covalent docking and mass spectrometry confirm a single site of GMD alkylation.

Structural Features and Nonlinear Rheology of Self-Assembled Networks of Cross-Linked Semiflexible Polymers.

Disordered networks of semiflexible filaments are common support structures in biology. Familiar examples include fibrous matrices in blood clots, bacterial biofilms, and essential components of cells and tissues of plants, animals, and fungi. Despite the ubiquity of these networks in biomaterials, we have only a limited understanding of the relationship between their structural features and their highly strain-sensitive mechanical properties. In this work, we perform simulations of three-dimensional networks produced by the irreversible formation of cross-links between linker-decorated semiflexible filaments. We characterize the structure of networks formed by a simple diffusion-dependent assembly process and measure their associated steady-state rheological features at finite temperature over a range of applied prestrains that encompass the strain-stiffening transition. We quantify the dependence of network connectivity on cross-linker availability and detail the associated connectivity dependence of both linear elasticity and nonlinear strain-stiffening behavior, drawing comparisons with prior experimental measurements of the cross-linker concentration-dependent elasticity of actin gels.

Strategies for controlling biofilm formation in food industry

Foodborne pathogen poses a threat to the food industries as many outbreaks have been found to be associated with biofilm formation. The formation of biofilm is a self-protection growth pattern of bacteria, which increases post-processing contamination and risk to public health. It is difficult to eliminate the biofilm in the food industries, since the biofilm cells have a barrier preventing or lessening the contact with environmental stresses, antimicrobial agents and the host immune system. Bacterial biofilm formation is a complex process, including initial attachment stage, irreversible attachment stage, biofilm development stage, biofilm maturation stage, and biofilm dispersion stage. The genetic mechanism, substratum and bacterial cell surface properties involve in the biofilm formation. The biofilm inhibition methods studied are physical treatment, chemical and biochemical treatment. The potential green and safe biochemical method attracts more attention, especially, the novel strategies using the safe biochemical agents (essential oils, enzymes, biosurfactants, others) constantly emerged. The review emphasized on effective strategies for inhibiting biofilm formation in different stages (initial irreversible attachment, formation, and maturation) by use of biochemical agents, aiming to provide new insight into biofilm control in food industry thus improving food quality and safety.

Multi‐Ionic Capacity of Zn‐Al/V6O13 Systems Enable Fast‐Charging and Ultra‐Stable Aqueous Aluminium‐Ion Batteries

AbstractRechargeable, cost‐efficient aqueous aluminium‐ion batteries (AAIBs) possess abundant trivalent charge carriers with high volumetric energy densities. However, the rapid and irreversible formation of Al2O3 passivation films on aluminium‐ion (AI) anodes while using aqueous electrolytes limits their development. Herein, Zn metal was used as the anode, and Al3+ was locally deposited on the Zn anode during charging. V6O13 with a mixed vanadium state of V4+/V5+ was chosen as the cathode because of its efficient ion diffusion (solid state) and high electron conductivity. The Zn−Al/3 M Al(OTF)3/V6O13 cell exhibited high current density and excellent long‐term cycling stability, demonstrating a very high specific capacity of ∼100 mAh g−1 at a current density of 3 A g−1 and Coulombic efficiency of ∼100 % with reversible stability over 1400 cycles. Furthermore, the V6O13 cathode exhibited a multi‐ionic capacity of Zn2+‐ and H+‐ions during the Al deposition/dissolution reaction in AAIBs, demonstrating high safety and stability for fast charging.

Reasons for low flowback behaviors of water-based fluids in tight sandstone gas reservoirs

Water-based working fluids are widely applied in the development of tight gas formations. However, these fluids’ flowback rate is generally low than 50%, resulting in a large amount of water retention to dramatically decline the gas delivery. Typical tight sandstone core samples are selected in this study to perform the gas-driven water displacement experiment to investigate the underlying mechanisms for the low water flowback behaviors in tight gas reservoirs. Results show that the average water flowback rate for 15 tight sandstone samples by gas-driven water displacement is obtained to be only 31.31%, which in turn causes an average gas permeability damage rate of 58.94%. Analysis suggests that multiscale pore structures, ultra-low connate water saturation phenomenon, filling of hydrophilic clay minerals, and insufficient pressure drop contribute to the congenitally unfavorable geological factors of low water flowback capacity. On the other hand, irreversible formation damages like water phase trapping, salting out issues, and residual water film effect caused by water retention are the main elements that restrict water removal during a gas-flow drying process. The findings of this study provide useful insights into the control mechanisms of low water flowback behaviors and the formation damages induced by water invasion in tight sandstone gas reservoirs.

Development of long lifespan high-energy aqueous organic||iodine rechargeable batteries

Rechargeable aqueous metal||I2 electrochemical energy storage systems are a cost-effective alternative to conventional transition-metal-based batteries for grid energy storage. However, the growth of unfavorable metallic deposition and the irreversible formation of electrochemically inactive by-products at the negative electrode during cycling hinder their development. To circumvent these drawbacks, herein we propose 3,4,9,10-perylenetetracarboxylic diimide (PTCDI) as negative electrode active material and a saturated mixed KCl/I2 aqueous electrolyte solution. The use of these components allows for exploiting two sequential reversible electrochemical reactions in a single cell. Indeed, when they are tested in combination with an active carbon-enveloped I2 electrode in a glass cell configuration, we report an initial specific discharge capacity of 900 mAh g−1 (electrode mass of iodine only) and an average cell discharge voltage of 1.25 V at 40 A g−1 and 25pm1 °C. Finally, we also report the assembly and testing of a PTCDI|KCl-I2|carbon paper multilayer pouch cell prototype with a discharge capacity retention of about 70% after 900 cycles at 80 mA and 25pm1 °C.

Mechanistic and kinetic insights into phenol-catalyzed cyclotrimerization of cyanate esters

Differential scanning and combustion calorimetry in combination with isoconversional methodology and chromatography are applied to acquire kinetic and mechanistic insights into the reaction of phenol-catalyzed cyclotrimerization of cyanate ester. The only detectable reaction intermediate is found to be imidocarbonate, which is demonstrated to form in an irreversible manner. Isoconversional analysis indicates that the overall reaction kinetics at its early and late stages is respectively controlled by the irreversible formation of imidocarbonate (Ea≈40 kJ mol−1) and a reaction of imidocarbonate with cyanate ester (Ea≈70 kJ mol−1). Cyclotrimerization of neat imidocarbonate is analyzed as well. For this reaction, no intermediates are detected. Its overall kinetics is determined to occur as a single autocatalytic step. It is concluded that cyclotrimerization of imidocarbonate does not amount to any significant competition to the reaction between imidocarbonate and cyanate ester.

Smoking as one of the predictors of the severity of the condition of patients suffering from a new coronavirus infection

The relationship between smoking and the lung damage volume in patients with a confirmed new coronavirus infection diagnosis, hospitalized in a temporary infectious hospital for the treatment of patients suffering from a new coronavirus infection and community-acquired pneumonia was evaluated. This was in the Odintsovo Districts Patriot Park of the Moscow region. Smoking cigarettes, both active and passive, as well as exposure to tobacco smoke on the body, are important upper and lower respiratory tract infection risk factors due to local immune response suppression. Nevertheless, data from a number of international studies indicate a significantly lower number of hospitalized smoking patients compared to non-smokers. These indicators were investigated as the percentage and degree of lung damage, smoking history, the number of cigarettes smoked per day, and the smoker's index. In the course of the study, the data on a smaller percentage of smokers admitted to inpatient treatment were confirmed in comparison with non-smokers and smokers in the general population. There was no statistically significant difference in the volume of lung damage between smoking and non-smoking patients according to the chest organs computed tomography. At the same time, there was an increase in the volume of lung tissue damage, depending on the smoking experience. This is apparently due to the irreversible changes formation in lung tissue against a long-term smoking background. The median age of smoking patients was 56 years with a variation from 46 to 68 years. The minimum and maximum ages were 29 and 82. The median lung lesion was 32% with a variation from 23% to 39%. The minimum and maximum lung damage is 10% and 40%, respectively. A moderate correlation was found between the smoking experience and the volume of lung damage. An increase in lung damage by 0.309% should be expected with an increase in smoking experience by one full year. There was also no statistically significant difference in the number of cigarettes smoked per day and the smokers index.

One-Pot Catalytic Synthesis of α-Tetrasubstituted Amino Acid Derivatives via In Situ Generation of N-Unsubstituted Ketimines

A one-pot catalytic synthesis of α-tetrasubstituted amino acid derivatives via in situ generation of N-unsubstituted ketimines is reported. Because of the irreversible formation of N-unsubstituted ketimines, the yields were higher than those generated under the conventional one-pot reaction conditions. This process prevents the need to isolate unstable N-unsubstituted ketimines with alkyl substituents and streamlines the synthesis of highly congested α-amino acid derivatives.

Highly defective Ti3CNTx-MXene-based fiber membrane anode for lithium metal batteries

Lithium metal batteries (LMBs) have attracted increasing attention owing to their high theoretical capacity and low reduction potential. However, safety concerns and their low coulombic efficiencies (CE) arising from the nonuniform and irreversible formation of Li dendrites on their anodes hinder their practical application. Here, we demonstrate that a highly defective titanium-carbonitride (Ti3CNTx)-MXene-based fiber membrane can function as a dendrite-free anode substrate for LMBs. The Ti3CNTx fiber membrane electrodes, prepared via the electrostatic self-assembly of Ti3CNTx flakes onto a glass-fiber membrane substrate, had a high surface area (∼276 m2 g−1), leading to a high CE of ∼99.1%, excellent cycling stability of more than 1000 cycles in a Li half-cell test, and high energy density (581.78 W h kg−1) and high power density (3008 W kg−1) in a Li-MXene-fiber/NCM622 full-battery test. This excellent cell performance is attributed to the strong lithiophilicity and high density of Ti vacancy defects in the Ti3CNTx MXenes, as well as the high surface area of the fiber membrane electrode. The lithiophilicity and defect structure of Ti3CNTx MXenes in LMB operation were elucidated by DFT calculations.

Photoswitching of Local (Anti)Aromaticity in Biphenylene-Based Diarylethene Molecular Switches.

Photoinduced tuning of (anti)aromaticity and associated molecular properties is currently in the focus of attention for both tailoring photochemical reactivity and designing new materials. Here, we report on the synthesis and spectroscopic characterization of diarylethene-based molecular switches embedded in a biphenylene structure composed of rings with different levels of local (anti)aromaticity. We show that it is possible to modulate and control the (anti)aromatic character of each ring through reversible photoswitching of the aryl units of the system between open and closed forms. Remarkably, it is shown that the irreversible formation of an annulated bis(dihydro-thiopyran) side-product that hampers the photoswitching can be efficiently suppressed when the aryl core formed by thienyl groups in one switch is replaced by thiazolyl groups in another.

Frontispiece: Isopropenyl Esters (iPEs) in Green Organic Synthesis

Isopropenyl esters (iPEs) and isopropenyl acetate (iPAc) are characterised by a tuneable reactivity in organic synthesis. Thanks to the irreversible formation of acetone in transesterification conditions, iPEs are eco-friendly acylating agents and can be employed for direct biomass modification and/or tandem esterification-acetalization reactions. C−C and C−X bond formation reactions occur selectively on the isopropenyl moiety via electrophilic and/or radical additions and/or metal- and/or photo-catalyzed cross-coupling reactions.

Quantitative NMR analysis of the kinetics of prenucleation oligomerization and aggregation of pathogenic huntingtin exon-1 protein

The N-terminal region of the huntingtin protein, encoded by exon-1 (httex1) and containing an expanded polyglutamine tract, forms fibrils that accumulate in neuronal inclusion bodies, resulting in Huntington's disease. We previously showed that reversible formation of a sparsely populated tetramer of the N-terminal amphiphilic domain, comprising a dimer of dimers in a four-helix bundle configuration, occurs on the microsecond timescale and is an essential prerequisite for subsequent nucleation and fibril formation that takes place orders of magnitude slower on a timescale of hours. For pathogenic httex1, such as httex1Q35 with 35 glutamines, NMR signals decay too rapidly to permit measurement of time-intensive exchange-based experiments. Here, we show that quantitative analysis of both the kinetics and mechanism of prenucleation tetramerization and aggregation can be obtained simultaneously from a series of 1H-15N band-selective optimized flip-angle short-transient heteronuclear multiple quantum coherence (SOFAST-HMQC) correlation spectra. The equilibria and kinetics of tetramerization are derived from the time dependence of the 15N chemical shifts and 1H-15N cross-peak volume/intensity ratios, while the kinetics of irreversible fibril formation are afforded by the decay curves of 1H-15N cross-peak intensities and volumes. Analysis of data on httex1Q35 over a series of concentrations ranging from 200 to 750 μM and containing variable (7 to 20%) amounts of the Met7O sulfoxide species, which does not tetramerize, shows that aggregation of native httex1Q35 proceeds via fourth-order primary nucleation, consistent with the critical role of prenucleation tetramerization, coupled with first-order secondary nucleation. The Met7O sulfoxide species does not nucleate but is still incorporated into fibrils by elongation.